Visual indicator for teletypewriter line-test key



Aug. 19, 1947.

w. HOlNKlS ET AL 2,425,803

VISUAL INDICATOR FORTELETYPEWRITER LINETEST KEY Filed Aug. 8, 1944 Pi 'zlntel 16' jl t 8 10 9 W, vvvvv Teletypewriterr INVENTORS BBerry WHbLv/mis,-12

- A TTORN Patented Aug. 19, 1947 VISUAL INDICATOR FOR TELETYPEWRITER LINE-TEST KEY William Hoinkis, Summit, and Donald B. Perry,

Maplewood, N. J., assignors to American Telephone and Telegraph Company, a corporation of New York Application August 8, 1944, Serial No. 548,604

2 Claims.

This invention relates to teletypewriter sets and particularly to an arrangement adapted to give a visual indication when the line-test key of the set is in either the line position or the test position.

In the operation of a teletypewriter system in which the messages are transmitted automatically by a perforated tape, it is customary for an operator of a teletypewriter set to perforate the tape while the teletypewriter set is in the test position,

that is to say, when it is disconnected from the line. After a message has been properly recorded on the tape, the set is connected to the line, by throwing the key that puts the sender in operation and also-by the manipulation of the line-test key. Thereafter, the sender proceeds to transmit the message over the line to the distant teletypewriter sets and simultaneously records the message upon the printer of the local teletypewriter set. By that operating procedure the transmission or the message is withheld until the message has been fully and correctly recorded upon the perforated tape. That procedure affords an opportunity to correct errors which otherwise would be transmitted if the set were connected to the line while the operator was typing the message, Furthermore, the operator is enabled to record the message upon the tape at a speed best suited to her which may not be, and probably would not be, the best speed for transmission of th message over the line; but once the message has been recorded upon the tape it may be transmitted automatically by the sender at the full speed at which the line is capable of transmitting.

Sometimes, through inadvertence or mistake, the operator, after throwing the key that puts the sender in operation, fails to throw the line-test key to the line position with the result that the message recorded on the tape will appear upon the printer of the local teletypewriter set but will not be transmitted to the line. The operator, upon seeing the message being printed upon the printer of her teletypewriter, may labor under the impression that it is also being transmitted over the line, when, in fact, such is not the case. In consequence, the message will not reach the distant teletypewriter station to which itis intended to be sent.

The object of the present invention is to insure against the loss of messages arising from the failure to operate the line-test key to the line position, when the operator intends to transmit a message, by providing an indicating device that will attract the operators attention and will indicate the position of that key.

This invention will be clearly understood from the following description when read in connection with the attached drawing that shows schematically a form of embodiment of the invention,

The apparatus shown within the dotted line designated I represents schematically a teletypewriter set which is adapted tobe connected to the line 2 by means of the line-test key 3, which in the drawing is shown in the test position. Connected to the line 2 at a distant point is a teletypewriter set 4, which is rep-resented symbolically by a relay 5 and a source of potential 5. The sending contacts I of the local teletypewriter set are connected to the swing contacts of the line-test key 3, the connection including a winding 8 of the line relay 9. That relay has a biasing winding l8 across which is bridged a source of potential I], which source is also connected to the inner contact points I? and I9 or the line-test key .3, the connection including a resistance element l2 across which is shunted a neon lamp I3 in series with a resistance M. The outer contact points 20 and 2| of the switch 3 are effectively connected to the sides of the line 2. The line, however, is closed through the contact I5 when the line-test key is in the test position, the purpose of which will later be made clear. A printin magnet I6 is connected to the contacts of the line relay 9.

The purpose of this invention and the manner in which that is accomplished will be clearly understood from the following description of the mode of operating the set. Let it be assumed that the line-test key 3 is in the test position as shown in the drawing. Current will thereupon flow from the source of potential II through the resistance element I2, contact I! of th key, winding 8 of relay 9, normally closed contact I8 of the sending contacts I, contact I 9 of the key and the opposite side of the source I I. Current will also flow from source ll through the biasing winding In of the line relay. The drop in potential across the resistance element I2 will cause the neon lamp I3 to glow'an will thus indicate to the operator that the line-test key is in testing position. The light of that lamp will remain steady until the operator begins to transmit the test message. That will, of course, open and close other contacts of the sending contacts I and the variation in current produced thereby in the resistance element l2 will cause the light of the lamp l3 to flicker. This condition of a steady light or a flickering light of the lamp I3 tends to impress upon the operator the knowledge of the fact that the line-test key 3 is in the test position.

When the operator is ready to transmit a message over the line, she will operate the line-test 3 key to the line position. That operation opens contacts I! and I9 and closes contacts 20 and 2|. The same operation also opens contact 15 which kept the line 2 normally closed while the local teletypewriter set was in the test position. The operation of the line-test key to the line position connects the sending contacts to the line through the contacts 20 and 2| of the line-test key and through the opening and closing of the sending contacts I, the impulses of the teletypewriter code are transmitted to the distant set 4. The opening of contacts I! and I9 opens the circuit that contains the source of potential I I, the resistance element l2 and the lamp l3, thereby extinguishing the light of that lamp. Accordingly, when the line-test key 3 is in line position, the neon lamp l3 will not be lighted.

The employment of a visual indicating device, such as a lamp, serves to insure the proper positioning of the line-test key and. thereby to prevent failure to transmit such messages which would occur if the operator fails to throw the key to the line position upon setting the sender in operation in order to transmit the message intended to be transmitted over the line. Furthermore, the presence of the signal improves the degree of supervision of the operators by the supervisory personnel.

While this invention has been described as embodied in a particular form, it is capable of embodiment in other and different forms without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. A teletypewriter set including a sender adapted to be connected to a line, a source of potential also connected with the said set, a switch having a plurality of contacts to connect the set to a line and disconnect it therefrom, a

sender.

resistance element connected between one of the contacts and one side of said sourc of potential, the other side of which is connected to another of the said contacts, and a visual indicating device bridged across the said resistance element and responsive to the voltage across the said elemerit to indicate whether the set is connected to the said line or is disconnected therefrom.

2. An arrangement to give a visual indication whether the line-test key of a teletypewriter set is in the line position or the test position comprising, in combination, a sourc of potential, a key to certain of the fixed contacts of which the said source is connected, the connection including a resistance element, a sender connected to the swing contacts of the said key, and a neon lamp bridged across the said resistance element and adapted to provide a steady glow when the said fixed and swing contacts of the key are closed in the test position, and to produce a flickering light in accordance with the operation of the said WILLIAM HOINKIS. DONALD B. PERRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,928,586 Blanton Sept. 26, 1933 1,921,990 Hewitt Aug. 8, 1933 1,733,609 Kuhn Oct. 29, 1929 2,082,924 Watson June 8, 1937 2,024,580 Kinkead Dec. 17, 1935 1,877,943 Motto Sept. 20, 1932 2,214,317 Bash Sept. 10, 1940 2,374,908 Weaver May 1, 1945 

